Some subterranean formations contain fluids, such as water, often at great pressure. When drilling a borehole through such formations, the fluid may flow out of the borehole, which causes safety problems for drilling personnel. These safety problems are increased when the fluid is at relatively high or low temperatures. In addition, in some drilling operations, a borehole is drilled in an upward direction from underground. In these cases, reaching fluids while drilling, which then do not even have to be pressurized, can result in large flows of these fluids in a tunnel from which drilling proceeds. Such flows have to be reduced or stopped rapidly to avoid potential flooding of the tunnel.
The prior art presents some drilling systems that include a valve to help mitigate the problems described hereinabove. However, they are not well adapted to some tasks, such as sample recovering samples from the borehole as the valve does not allow passage of conventional sample recovering accessories therethrough. Also, they are often relatively complex as they include control systems allowing selective operation of the valve between open and closed configurations by an operator.
Against this background, there exists a need in the industry to provide improved systems, devices and method allowing access to a distal end of a borehole even when the borehole is drilled though fluid containing formations.
An object of the present invention is therefore to provide such systems, devices and methods.